The Linux Administration group is for the discussion of technical issues technical issues that arise during the administration of Linux systems, including maintaining the operating system and supporting end-user applications.

You can't tell from within any operating system. You can only reliably tell by looking at the markings on the cable itself, if there are any. If you are running a 10/100 network, then there is no difference whatsoever between cat 5, 5e, and 6. There's only a difference if you are running a gigabit network. If you are running a gigabit network, cat 5 and 5e cables could cause slowdowns and errors.

If you are running a standard 10/100 network and are experiencing slow network performance, it is probably not the cables themselves. Rather, you may need to take a close look at your network architecture.

The difference between cat5,+sub class to cat6,+sub? Is not that great. The biggest issue after cat 5 is found in crosstalk and read errors at the furthest limits of the cable media.

I would suggest you look at how you have sub netted your network. Collisions are a great problem when you do not maintain reasonable sizes for subnets. Just because you feel the need to have old style Class A or B domain - giving you a larger number of nodes (IP addresses) ? don't mean the subnet can route within the subnet - efficiently. It may be necessary to install boundaries within the same subnet or you will still have connection/interference issues. You may need to isolate conflicts and collisions domains, by using network devices to make things more efficient: Switches and/or routers can assist you in making your subnet more responsive, so can reviewing your architecture. ( When Accounting moved to the second floor or development was out sourced - you might need to rethink your addressing scheme - it may not be advisable to keep the same IP addresses out of habit or because you didn't want to go through the hassle of changing them?)

As others have mentioned - most in-house LAN/WAN (networks are running at 100 or still at 10) ? folks just don't type fast enough to warrant giga-bit desktop - unless your clients are doing a lot of downloading between different sites over the internet.

I would check cabling. If something has happened to the electrical characteristics of a cable or connection you could see the symptoms you describe. You can purchase a tester to see if the cable, connectors and connections are working within specification. (make sure the tester tests for cross talk)

Has anyone added a cable to your system ?
Has anyone moved a cable on your system?

This could mean that the added cable was bad or the moved cable was damaged

Has anyone damaged the connector on a patch panel , switch or hub or wall connector?

The transmission properties of a Cat 5 cable will change if there:

Is two much of a twist at the cable head. (please read specifications for cat 5 cables)
If one of the tx or rx lines are nicked.
If the connector in a wall plate have come out of position.

I would start with a known good cable, and connect device and start from there.

I am quite surprised that this discussion has taken so long to get to the physical possibilities.

Using cat anything implies that there are switches routers, etc. in the network and all cabling is point to point.
If the whole network is slow, this would indicate that there is a conflict in the configuration something like a duplicate address or other routing error.
An improperly constructed cable, where the plugs are not correctly configured, would do it for only one segment.
Bad switch rules or configuration would cause the whole network to "go slow" due to timeouts or bandwidth bottlenecks. Vlan configuration could slow a network to a crawl.
First thing that must be done is test point to point communications and try to isolate where the problem is affecting and then try to isolate and define the real problem.
Sorry I cannot be more specific, but there are just to many variables at this time.

It is not possible to determine it through the OS, Most cables are labeled. I agree with Jalal other network bottlenecks can be checked in the list provided by Jalal
To improve network speed alot of things have to be taken care of which includes Network Adaptors, Switches and Routers. What it means is that you cannot only change one medium and expect to improve speed. If you want to run a gigabit Network then you need to make sure your network Adaptors Supports Gigabit, and so are the Switches. If one PC in the Network does not support this it could affect performance of other machines especially where the communication is involving the slow Network Adaptor to accommodate it in the communication the fast Adaptors to needs to Negotiate the exchange of frames in the same wave length.

Reply from skq01 on Aug 11 at 3:37 PM I personally don't see how one can determine the physical cable type (ie cat5, cat5e, cat6) from the OS ... I've
always had to eyeball the physical cable and note what is printed there ...

Are your switches capable of gigabit speeds? If not, CAT6 is doing nothing for you.
If you have a linux box, load up EtherApe. You can quickly visually see where your bandwidth is being used up.
If you have no nodes using excessive bandwidth, look for collision domain issues caused by hubs existing on your network.
If you have no collision issues, look for statically assigned IP addresses conflicting with DHCP. Be sure every device has a proper DNS entry and all static IPs are given reservations.
If you have no IP conflicts, try to determine if it is your web gateway and internet traffic which is slow or if it is LAN data transfer that is slow by checking file transfer speeds on the WAN and LAN.
If the problem is with your LAN, you need to look at each switch and router to ensure proper setup and functionality. While you are on the switches, check for ports with high error rates as that is a good indication of a bad cable.

Hello V, lots of good points have been made already; just enough to point you in the right direction. This problem is most likely a physical or layer 1 problem. If you are still stuck, here are my suggestions:
1. Check the patch cables carefully be sure none is looped back into the switch i.e switch port to switch port! An honest mistake but can be quite costly; you might not be able to forward traffic at all.
2. If the cabling is fine try substituting each of the other devices and note the change in performance
Good luck

Sometime, due to environment problems (such as particularly strong magnetic
fields close to the cables), is it possible to experience network issues
like slowness. If this is the case and is not possible to avoid the
environment problem a fiber optic cable network is to be considered as a
possible alternative.